Conveners
Structure of Hadrons and Nuclei
- Huey-Wen Lin (MSU)
Structure of Hadrons and Nuclei
- Takeshi Yamazaki (Univerity of Tsukuba)
Structure of Hadrons and Nuclei
- Nikhil Karthik (BNL)
Structure of Hadrons and Nuclei
- Martha Constantinou (Temple University)
Structure of Hadrons and Nuclei
- Peter Petreczky (Brookhaven National Lab)
Structure of Hadrons and Nuclei
- Jeremy Green (DESY, Zeuthen)
Structure of Hadrons and Nuclei
- Lasse Mueller (Goethe University Frankfurt)
We update our calculation of flavor diagonal nucleon axial, scalar and tensor charges on eight 2+1+1-flavor MILC HISQ ensembles using Wilson-clover fermions. We discuss the signal in the sum of the connected and disconnected contributions for the up, down and strange quarks, control over fits to remove excited state contamination, the simultaneous chiral-continuum fit used to extract the...
The axial charge of the nucleon, $g_A$, has been computed extensively on the lattice. However, the axial charges for other octet baryons (hyperons) such as the $\Sigma$ and $\Xi$ baryons are less well known experimentally and theoretically.
Here we present results for the isovector axial, scalar and tensor charges, as well as for the second Mellin moments of isovector PDFs. This allows us...
We present results from the QCDSF/UKQCD/CSSM collaboration for the charges g_T, g_A and g_S of the baryon octet, obtained through the use of Feynman-Hellmann techniques. We use a flavour symmetry breaking method to systematically approach the physical quark mass using ensembles that span five lattice spacings and multiple volumes. We extend this existing flavour breaking expansion to also...
A lot of progress has been made in the direct determination of nucleon sigma terms. Using similar methods we consider the sigma terms of the other octet baryons as well. These are determined on CLS gauge field ensembles employing the Lüscher-Weisz gluon action and the Sheikholeslami-Wohlert fermion action with $N_\mathrm{f} = 2 + 1$. The ensembles analysed here have pion masses ranging from...
We report preliminary results from an analysis of the pion scalar form factor computed on a set of the $\mathrm{tr}[M]=\mathrm{const}$ CLS gauge ensembles with $N_f=2+1$ Wilson Clover-improved sea quarks. The calculations are carried out for light quarks masses corresponding to $M_\pi\approx 0.130\mathrm{MeV} \ldots 350\mathrm{MeV}$, four values of the lattic spacing...
Traditionally, there has been a method to analyze the charge radius of the hadron based on the fits of its form factor with some model assumptions. Moreover, a completely different method has been proposed, which does not depend on the models. In this presentation, we explore several improvements to this model-independent method for analyzing the pion charge radius. Furthermore, we compare the...
We present results for the electromagnetic form factors of the proton and neutron computed on the $(2 + 1)$-flavor Coordinated Lattice Simulations (CLS) ensembles including both quark-connected and -disconnected contributions. The $Q^2$-, pion-mass, lattice-spacing, and finite-volume dependence of our form factor data is fitted simultaneously to the expressions resulting from covariant chiral...
We present results of nucleon structure studies measured in 2+1 flavor QCD with the physical light quarks in a large spatial extent of about 10 fm. Our calculations are carried out with the PACS10 gauge configurations generated by the PACS Collaboration with the stout-smeared $O(a)$ improved Wilson fermions and Iwasaki gauge action at $\beta$=1.82 and 2.00 corresponding to the lattice spacings...
The Deep Underground Neutrino Experiment (DUNE) is an upcoming neutrino oscillation experiment that is poised to answer key questions about the nature of the neutrino. Lattice QCD has the ability to make significant impact upon DUNE by computing the interaction of a nucleon to a weak current. Nucleon amplitudes involving the axial form factor are part of the primary signal measurement process...
The current status of lattice-QCD numerical calculations by joint LHP and RBC collaborations of nucleon isovector vector- and axialvector-current form factors using a 2+1-flavor dynamical domain-wall fermions lattice QCD ensemble generated jointly by RBC and UKQCD collaborations will be presented. The lattice spacing is set at about 0.1141(3) fm, and the lattice spatial extent is 48 spacings...
Proton and neutron electric and magnetic form factors are the primary characteristics of their spatial structure and have been studied extensively over the past half-century. At large values of the momentum transfer $Q^2$ they should reveal transition from nonperturbative to perturbative QCD dynamics and effects of quark orbital angular momenta and diquark correlations. Currently, these form...
In lattice-QCD calculations of parton distribution functions (PDFs) via large-momentum effective theory, the leading power (twist-three) correction appears as ${\cal O}(\Lambda_{\rm QCD}/P^z)$ due to the linear-divergent self-energy of Wilson line in quasi-PDF operators. For lattice data with hadron momentum $P^z$ of a few GeV, this correction is dominant in matching, as large as 30\% or more....
We present recent updates on the lattice calculations of the valence-quark GPDs of the pion, the pion and kaon gluon PDF, and their first gluon moment in the physical-continuum limit. All these calculations are done on ensembles with $N_f = 2 + 1 + 1$ highly improved staggered quarks (HISQ), generated by the MILC Collaboration. The valence-quark GPD of the pion is done at lattice spacing...
The Light-Cone Distribution Amplitude (DA) encodes the non-perturbative information of the leading Fock-component of the hadron wave function, therefore required for processes including exclusive hadron production. As the Pseudo-Nambu-Goldstone boson of QCD, nonperturbative structure of the pion is of particular interest. We present a lattice QCD calculation of the pion DA on ensembles with...
The light-cone distribution amplitude (LCDA) of the pion carries information about the parton momentum distribution and is an important theoretical input into various predictions of exclusive measurements at high energy, including the pion electromagnetic form factor. We provide constraints on the fourth Mellin moment of the LCDA using the heavy quark operator product expansion (HOPE) method.
In this talk, we will discuss a new method to calculate parton distribution functions (PDFs) from correlations of boosted quarks and gluons in the Coulomb gauge.
Compared to the widely used quasi-PDFs defined from gauge-invariant Wilson-line operators, such correlations offer advantages including absence of linear power divergence, enhanced long-range precision, and accessibility to larger...
We present an update on our lattice calculations of the Mellin moments of PDFs and GPDs for the pion and kaon, using momentum-boosted meson states. In particular, we focus on the calculation of the scalar and tensor local operators, as well as the vector operator with up to three-covariant derivatives. The corresponding matrix elements allow us to extract the scalar and tensor charges, as well...
The gravitational form factors (GFFs) of hadrons are related to the second Mellin moments of their generalized parton distributions. They can be extracted from matrix elements of the energy-momentum tensor of QCD. We present the gluon and quark flavor contributions to the GFFs of the pion and the nucleon in the kinematic region $0 \leq -t \leq 2~\text{GeV}^2$ on a clover improved ensemble with...
The trace of the energy momentum tensor (ETM) in the hadron gives the hadron mass. The trace anomaly due to the conformal symmetry breaking is believed to be an important ingredient for confinement. In this talk, I will show the trace anomaly form factors of the pion, nucleon and $\rho$ meson as functions of the squared momentum transfer $Q^2$ up to $\sim 4.3~\mathrm{GeV}^2$ which are...
Quark orbital angular momentum in the proton is evaluated via a Lattice QCD calculation of the second Mellin moment of the twist-3 generalized parton distribution $\widetilde{E}_{2T} $ in the forward limit. The connection between this approach to quark orbital angular momentum and approaches previously utilized in Lattice QCD calculations, via generalized transverse momentum-dependent parton...
Recently, significant progress has been made in improving the efficiency and computational speed of lattice QCD calculations associated with Generalized Parton Distributions (GPDs). These advancements are a result of employing asymmetric frames, which differ from the commonly used symmetric frames, and introducing flexibility in the distribution of transferred momentum. A key element of our...
First lattice QCD calculations of x-dependent GPD have been performed in the Breit frame, where the momentum transfer is evenly divided between the initial and final hadron states. Employing the asymmetric frame proposed in PRD 106 (2022) 11, 114512, we are able to obtain proton GPDs for multiple momentum transfers in a computationally efficient setup. In this presentation, we focus on the...
Generalized parton distribution functions (GPDs) describe the longitudinal momentum distribution within a hadron among its constituent partons as well as information about the momentum in the transverse direction. We calculate unpolarized and helicity GPDs using 2+1+1 flavors of highly improved staggered quarks in ensembles generated by the MILC collaboration at a=0.09 fm with a physical pion...
Generalized Parton Distributions (GPDs) are related to one aspect of nucleon tomography, the 3D imagining the proton. In one limit, the GPD can describe both the longitudinal momentum and the transverse position of a parton. In other limits, the GPD can describe how each parton contributes to the total spin or mass of the nucleon. Nucleon tomography has sparked great interest as a goal of many...
Understanding the intricate three-dimensional internal structure of the nucleon has been a long-standing challenge. The main quantitative tool to map this structure are the generalized parton distributions (GPDs). In this talk, we present the first extraction of unpolarized GPDs using the pseudo-distribution approach on the lattice. We use one ensemble of $N_f=2+1+1$ twisted mass fermions at a...
We present the first lattice calculation of the four twist-3 axial quark GPDs for the proton in the $N_f=2+1+1$ twisted-mass formulation with a clover improvement. The ensemble has a volume $32^3\times64$, lattice spacing 0.0934 fm, and corresponds to a pion mass of 260 MeV. The calculation used the quasi-GPDs approach, which requires matrix elements with momentum-boosted proton states coupled...
The TMD soft function may be obtained by formulating the Wilson line in terms of auxiliary 1-dimensional fermion fields on the lattice. In the "timelike" region, this corresponds to the moving heavy quark effective theory (HQET). I present the results of the one-loop calculation of the Euclidean space analog to the soft function, and show that it must proceed in the "spacelike" region....
This work presents a determination of the quark Collins-Soper kernel, which relates transverse-momentum-dependent parton distributions (TMDs) at different rapidity scales, using lattice quantum chromodynamics (QCD). This is the first lattice QCD calculation of the kernel at quark masses corresponding to a close-to-physical value of the pion mass, with next-to-next-leading logarithmic matching...
We present one-loop perturbative results of the renormalization functions for a complete set of nonlocal quark bilinear operators containing an asymmetric staple-shaped Wilson line, using a family of improved lattice actions. This study is relevant for the nonperturbative investigations regarding the renormalization of the unpolarized, helicity and transversity transverse-momentum dependent...
In this study, we investigate renormalization of gauge-invariant nonlocal gluon operators up to one-loop in lattice perturbation theory. Our computations have been performed in both Dimensional and lattice regularizations, using the Symanzik improved gluon action, leading to the renormalization functions in the modified Minimal Subtraction $(\overline{MS})$ scheme, as well as conversion...
We study effects of gauge smearing on the nucleon and meson gluon-PDF matrix elements, considering hypercubic smearing, stout smearing, and Wilson flow. The lattice calculations are carried out with $N_f = 2 + 1 + 1$ highly improved staggered quarks in ensembles generated by the MILC Collaboration. We use clover fermions for the valence action on one lattice spacing $a \approx 0.12$ fm and...
The electromagnetic polarizability is an import property of nucleon. It describes the reponse of a nucleon when it is placed in an external eletric or magnetic field. The polarizability can be extracted from the real or virtual Compton scattering process γN → γN. We develop a method to calculate the the Compton scattering matrix elements of nucleon from a 4-point correlation function on the...
We explore a general method based on four-point functions in lattice QCD. The electric polarizability ($\alpha_E$) of a charged pion has been determined from the method in a previous simulation. Here we focus on the magnetic polarizability ($\beta_M$) using the same quenched Wilson action on a $24^3\times 48$ lattice at $\beta=6.0$ with pion mass from 1100 to 370 MeV. The results from the...
The dominant contribution to the theoretical uncertainty in the extracted weak parameters of the Standard Model comes from the hadronic uncertainties in the electroweak boxes, i.e. $\gamma-W^\pm/Z$ exchange diagrams. A dispersive analysis relates the box diagrams to the parity-odd structure function, $F_3$, for which the experimental data either do not exist or belong to a separate isospin...
The excitation of nucleons to resonance structures via electromagnetic interactions is crucial for enhancing our comprehension of strong interactions within the realm of quark confinement. Additionally, accurate knowledge of neutrino-nucleon scattering is vital for neutrino oscillation experiments. In this study, we present determinations of the nucleon electric form factor ($G_E(Q^2)$), the...